Breathing new life into the 318 in the Scamp!

Right.

The 340 cam was a .444 lift.

I'll probably check it with a micrometer at the valve spring retainer through 15-5 BTDC and again @ 5-15 ATDC to get a map of lift clearance acrossed the piston crank angle.

I don't think I'll need to clay check if I just use a set of check springs on #1.

The reason I think there was so much garbage in timing with the engine was because this engine ate up 2 timing chains over the course of 170K.

Someone had been inside it and replaced the factory unit with another single roller. I found plastic timing gear shrapnel in the pickup screen and an insane amount of slop in the chain I pulled from it. I was able to move the cam about 12 degrees back and fourth on the old chain. That's double in slop on crank angle! I could only imagine what the original set looked like at the point that it was replaced.

Hughes calls for a minimum of .060" clearance on intake valve to piston and .100" exhaust valve to piston. If I don't see those numbers at each degree of the crank where it's critical, when I check actual lift before assembly, I think I'll just notch them where I need to with a fixture.

Hopefully I won't have to. I know that I have the clearance on the guide end for everything, without factoring in pushrod angle loss in total lift, as well as factory rocker loss in lift ratio. I stuck to 1.5:1 numbers and made sure I had at least that on the top end.

I'll measure actual lift and report that number here, as well as clearance against each degree of crank angle with a light valve spring, so I can over extend the rocker at each degree on the crank until the valve touches, then write the difference down. If anything is less than spec, that should tell me.

The reason I don't think I'll have issues is that max lift on this cam is shorter in it's open span. The duration number is more than a 318, but less than 340, so the piston chasing the valves won't be nearly as abrasive as even a stock 340 spec cam.

I'll have to check and see what's in the 318 running a 340 cam in the '72 outside through a plug hole. I'd be curious, but I know people have run 340 spec duration on stock 318 engines without any issues.

It does depend on the piston, though.

The numbers will tell the truth on this one, once I get my gear back from the machinist, today.